Investigation of In-Situ and Laboratory Hydraulic Fracturing Tests in Uma Oya Hydropower Project-Sri Lanka

This paper presents results from in-situ and laboratory hydraulic fracturing tests completed for Uma Oya Hydropower Project in Sri Lanka .Generally, from pressuretimecurves obtained in underground field hydraulic fracture tests one can determine the breakdown pressure Pc, the fracture reopening pressure Pr, the shut-in pressurePs and in-situ hydraulic tensile strength of rock Pco. These pressure values are then used for the calculation of the in situ stress state. In this paper we present a method ofmeasurement of the hydraulic tensile strength of rock in laboratory conditions for firsttime in Iran. In laboratory experiments to determine the value of tensile strength, the rock samples were subjected to axial stress and confining pressure. Internalpressurization was achieved by injection of water into the 4 mm diameter holes at a rate of 1ml/s. Fracture initiation and dynamic fracture growth is characterized by ahydraulic short circuit between axial stress, confining pressure and injection pressure,which yields the breakdown pressure Pc. Finally, we compare our results obtainedfrom laboratory conditions with the results obtained from the in-situ hydraulicfracture tests.

کلیدواژه ها:

Sri Lanka ، Hydraulic fracturing ، Laboratory experiment ، Tensile strength ، Breakdown pressure